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ARS Home » Southeast Area » Gainesville, Florida » Center for Medical, Agricultural and Veterinary Entomology » Chemistry Research » Research » Publications at this Location » Publication #138819
Title: DIFFERENTIAL ACTIVITY AND DEGRADATION OF PLANT VOLATILE ELICITORS PRESENT IN THE REGURGITANT OF TOBACCO HORNWORM (MANDUCA SEXTA) LARVAE

Author
item ALBORN, HANS - ENT DEPT, UNIV FLA
item Brennan, Margaret
item Tumlinson Iii, James

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2003
Publication Date: N/A
Citation: N/A

Interpretive Summary: Plants respond to insect herbivory by emitting volatile compounds that attract natural enemies of the herbivores. Tobacco hornworm regurgitant contains compounds, called elicitors, that are made by attaching different amino acids to fatty acids. These elicitors induce plants to activate defenses against insect attack. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA-ARS, Gainesville FL and University of Florida have been studying how these insect produced elicitors are made by the tobacco hornworm. They have found that different dietary sources fed to caterpillars did not change the amino acid composition of the fatty acid-amino acid conjugates in the regurgitant. They also found that only two compounds in the regurgitant are elicitors despite the presence of a number of similar compounds. The most active elicitor, N¿linolenoyl-L-glutamine found in the regurgitant of several other Lepidopteran larvae, is a relatively minor component in THW regurgitant because it is degraded rapidly. The elicitor present in greatest amount in THW regurgitant, N-linolenoyl-L-glutamic acid, degraded at a much slower rate. The results of this research demonstrate that great care must be taken when the FAA conjugates from different insects are analyzed, both qualitatively and quantitatively, and that it might not be possible to correlate those results with plants responses to different herbivorous insects.

Technical Abstract: Plants respond to insect herbivory by emitting volatile compounds that attract natural enemies of the herbivores. Using a standardized corn seedling bioassay, components of tobacco hornworm (THW) regurgitant were investigated for their efficacy as elicitors of volatiles. Two components, that elicited the strongest release of volatiles, were isolated and identified as N¿linolenoyl-L-glutamine (18:3-GLN) and N-linolenoyl-L-glutamic acid (18:3-GLU). The approximately 10 times more active 18:3-GLN that also can be found in the regurgitant of several other Lepidopteran larvae, was rapidly degraded when THW regurgitant was left at room temperature, while 18:3-GLU degraded at a much slower rate. Different dietary sources of THW and tobacco bud worm larvae consisting of both host and non-host plants did not reflect on the amino acid composition of the fatty acid-amino acid conjugates in the regurgitant.